In a Next Generation Network (NGN), service control is separated from the transport function, and a concept of resource admission control is introduced to ensure Quality of Service (QoS) of a service. A Resource and Admission Control Function (RACF) is located on the transport control layer between the service control layer and the transport bearer layer, as shown in FIG. 1. Through resource admission control, the details of the transport network are shielded from the service control layer, service control can be separated from the transport function, and the state of using resources of the transport network can be perceived downward. Through admission and resource control, the transport network resources can be utilized appropriately, the QoS of the service can be ensured, and theft of bandwidth and services can be prevented.
A resource admission control method that supports mobility is provided in the prior art. As shown in FIG. 2, the method includes:
Step 201: Before a mobile user moves to the current access network, a deregistration request is sent to a Service Control Function (SCF) at the application service layer.
Step 202: After receiving the deregistration request from the mobile user, the SCF sends a resource release request to RACF1 in the previous access network to which the mobile user attaches before handover, requesting to release resources in the previous transport network before handover of the mobile user.
Step 203: RACF1 releases resources of the previous transport network before the handover of mobile user.
Step 204: The mobile user moves to the current access network and then sends a registration request to the SCF.
Step 205: The SCF sends a service request to RACF2 in the current access network. The service request carries network resource parameters of the mobile UE, for example, QoS parameter.
Step 206: According to the network resource parameters of the mobile UE, RACF2 allocates resources to the transport network to which the mobile UE currently attaches.
In the process of researching and practicing the prior art, the inventor of the present invention finds at least the following problems in the prior art:                1. In the prior art, after the mobile user is authenticated, a request for accessing the SCF service is initiated from the mobile user side, and the SCF triggers the resource admission control, which slows down the resource allocation and release.        2. In the prior art, after the mobile user handover to another network, the SCF sends a service request to RACF2, and RACF2 enforces the corresponding policy on the current access network. Therefore, the QoS of the service is not ensured during the handover process, and therefore the continuity of a session can not ensured.        